It took me a good year to get anything useable. At the 4 month mark I had nothing, so you're way ahead of where I was.
"Take as needed" is pretty vague. I think the conventional wisdom is to take it regularly as a therapeutic aid to keep the blood flowing. Maybe every other day. I think maybe you didn't give the Cialis enough time, but it wouldn't hurt to give Viagra a try. Perhaps Viagra will provide better results.
Buy generic and save yourself some money.
Dave